Resistor material with metal component for use in circuitized substrates, circuitized substrate utilizing same, method of making said ciruitized substrate, and information handling system utilizing said ciruitized substrate

ABSTRACT

A material for use as part of an internal resistor within a circuitized substrate includes a polymer resin and a quantity of nano-powders including a mixture of at least one metal component and at least one ceramic component. The ceramic component may be a ferroelectric ceramic and/or a high surface area ceramic and/or a transparent oxide and/or a dope manganite. Alternatively, the material will include the polymer resin and nano-powders, with the nano-powders comprising at least one metal coated ceramic and/or at least one oxide coated metal component. A circuitized substrate adapted for using such a material and resistor therein and a method of making such a substrate are also provided. An electrical assembly (substrate and at least one electrical component) and an information handling system (e.g., personal computer) are also provided.

CROSS REFERENCE TO CO-PENDING APPLICATIONS

In Ser. No. 11/031,074, entitled Capacitor Material With Metal ComponentFor Use IN Circuitized Substrates, Circuitized Substrate Utilizing Same,Method Of Making Said Circuitized Substrate, and Information HandlingSystem Utilizing Said Circuitized Substrate”, filed Jan. 10, 2005(inventors: M. Poliks et al), there is defined a material for use aspart of an internal capacitor within a circuitized substrate whichincludes a polymer resin and a quantity of nano-powders including amixture of at least one metal component and at least one ferroelectricceramic component, the ferroelectric ceramic component nano-particleshaving a particle size substantially in the range of between about 0.01microns and about 0.9 microns and a surface area within the range offrom about 2.0 to about 20 square meters per gram. A circuitizedsubstrate adapted for using such a material and capacitor therein and amethod of making such a substrate are also provided. An electricalassembly (substrate and at least one electrical component) and aninformation handling system (e.g., personal computer) are also provided.This application is assigned to the same assignee as the presentinvention.

The present application is a continuation-in-part of Ser. No. 11/031,074filed Jan. 10, 2005.

In Ser. No. 11/031,085, entitled “Capacitor Material For Use InCircuitized Substrates, Circuitized Substrate Utilizing Same, Method ofMaking Said Circuitized Substrate, And Information Handling SystemUtilizing Said Circuitized Substrate”, filed Jan. 10, 2005 (inventors:J. Lauffer et al) under Attorney's Docket Number EI-2-04-017, there isdefined a material for use as part of an internal capacitor within acircuitized substrate wherein the material includes a polymer resin anda quantity of nano-powders of ceramic material having a particle sizesubstantially in the range of between about 0.01 microns and about 0.90microns and a surface area for selected ones of said particles withinthe range of from about 2.0 to about 20 square meters per gram. Acircuitized substrate adapted for using such a material and capacitortherein and a method of making such a substrate are also provided. Anelectrical assembly (substrate and at least one electrical component)and an information handling system (e.g., personal computer) are alsoprovided. This application is assigned to the same assignee as thepresent invention.

In Ser. No. 10/900,385, entitled “Circuitized Substrate With InternalOrganic Memory Device, Method Of Making Same, Electrical AssemblyUtilizing Same, and Information Handling System Utilizing Same” andfiled Jul. 28, 2004 (inventors: S. Desai et al), there is defined acircuitized substrate comprised of at least one layer of dielectricmaterial having an electrically conductive pattern thereon. At leastpart of the pattern is used as the first layer of an organic memorydevice which further includes at least a second dielectric layer overthe pattern and a second pattern aligned with respect to the lower partfor achieving several points of contact to thus form the device. Thesubstrate is preferably combined with other dielectric-circuit layeredassemblies to form a multilayered substrate on which can be positioneddiscrete electronic components (e.g., a logic chip) coupled to theinternal memory device to work in combination therewith. An electricalassembly capable of using the substrate is also provided, as is aninformation handling system adapted for using one or more suchelectrical assemblies as part thereof. This application is assigned tothe same assignee of the present invention.

In Ser. No. 10/900,386, entitled “Electrical Assembly With InternalMemory, Circuitized Substrate Having Electrical Components PositionedThereon, Method Of Making Same, And Information Handling SystemUtilizing Same” and filed Jul. 28, 2004 (inventors: F. Egitto et al),there is defined an electrical assembly which includes a circuitizedsubstrate comprised of an organic dielectric material having a firstelectrically conductive pattern thereon. At least part of the dielectriclayer and pattern form the first, base portion of an organic memorydevice, the remaining portion being a second, polymer layer formed overthe part of the pattern and a second conductive circuit formed on thepolymer layer. A second dielectric layer if formed over the secondconductive circuit and first circuit pattern to enclose the organicmemory device. The device is electrically coupled to a first electricalcomponent through the second dielectric layer and this first electricalcomponent is electrically coupled to a second electrical component. Amethod of making the electrical assembly is also provided, as is aninformation handling system adapted for using one or more suchelectrical assemblies as part thereof. This application is also assignedto the same assignee as the present invention.

TECHNICAL FIELD

The present invention relates to providing resistors within circuitizedsubstrates such as printed circuit boards, chip carriers and the like,and more specifically to a method for doing so and to products includingsuch internal components as part thereof. Even more particularly, theinvention relates to such methodologies and products wherein theresistors are comprised of nano-powders.

BACKGROUND OF THE INVENTION

Circuitized substrates such as printed circuit boards (hereinafter alsoreferred to as PCBs), chip carriers, and the like typically areconstructed in laminate form in which several layers of dielectricmaterial and conductive material (laminates) are bonded together usingrelatively high temperature and pressure lamination processes. Theconductive layers, typically of thin copper or copper alloy, are usuallyused in the formed substrate for providing electrical connections to andamong various devices located on the surface of the substrate, examplesof such devices being integrated circuits (semiconductor chips) anddiscrete passive devices, such as capacitors, resistors, inductors, andthe like. The discrete passive devices occupy a high percentage of thesurface area of the completed substrate, which is undesirable from afuture design aspect because of the increased need and demand forminiaturization in today's substrates and products containing same art.In order to increase the available substrate surface area (also oftenreferred to as “real estate”), there have been a variety of efforts toinclude multiple functions (e.g. resistors, capacitors and the like) ona single component for mounting on a board. When passive devices are insuch a configuration, these are often referred to collectively andindividually as integral passive devices or the like, meaning that thefunctions are integrated into the singular component. Because of suchexternal positioning, these components still utilize, albeit less thanif in singular form, board “real estate.” In response, there have alsobeen efforts to embed discrete passive components within the board, suchcomponents often also referred to as embedded passive components. Acapacitor or resistor designed for disposition within (e.g., betweenselected layers) a PCB (board) substrate may thus be referred to as anembedded integral passive component, or, more simply, an embeddedresistor or capacitor. Such a capacitor thus provides internalcapacitance while a resistor provides internal resistance. The result ofthis internal positioning is that it is unnecessary to also positionsuch devices externally on the PCB's outer surface(s), thus savingvaluable PCB surface area.

As defined in co-pending application Ser. No. 11/031,074 (relating toproviding internal capacitors), for a fixed capacitor area, two knownapproaches are available for increasing the planar capacitance(capacitance/area) of an internal capacitor. In one such approach,higher dielectric constant materials can be used, while in a second, thethickness of the dielectric can be reduced. These constraints arereflected in the following formula, known in the art, for capacitanceper area:C/A=(Dielectric Constant of Laminate×Dielectric Constant inVacuum/Dielectric Thickness)where: C is the capacitance and A is the capacitor's area.

Some of the patents listed below, particularly U.S. Pat. No. 5,162,977,mention use of various materials for providing desired capacitancelevels under this formula, and many mention or suggest problemsassociated with the methods and resulting materials used to do so.

As stated in Ser. No. 11/031,074, there have been past attempts toprovide internal capacitance and other internal conductive structures,components or devices (one good example being internal semiconductorchips) within circuitized substrates (PCBs), some of these including theuse of nano-powders. The following are some examples of such attempts,including those using nano-powders and those using alternative measures.

In U.S. Pat. No. 6,704,207, entitled “Device and Method for InterstitialComponents in a Printed Circuit Board”, issued Mar. 9, 2004, there isdescribed a printed circuit board (PCB) which includes a first layerhaving first and second surfaces, with an above-board device (e.g., anASIC chip) mounted thereon. The PCB includes a second layer having thirdand fourth surfaces. One of the surfaces can include a recessed portionfor securely holding an interstitial component. A “via”, electricallyconnecting the PCB layers, is also coupled to a lead of the interstitialcomponent. The described interstitial components include components suchas diodes, transistors, resistors, capacitors, thermocouples, and thelike. In what appears to be the preferred embodiment, the interstitialcomponent is a resistor having a similar size to a “0402” resistor(manufactured by Rohm Co.), which has a thickness of about 0.014 inches.

In U.S. Pat. No. 6,616,794, entitled “Integral Capacitance For PrintedCircuit Board Using Dielectric Nanopowders” and issued Sep. 9, 2003,there is described a method for producing integral capacitancecomponents for inclusion within printed circuit boards in whichhydro-thermally prepared nano-powders permit the fabrication ofdielectric layers that offer increased dielectric constants and arereadily penetrated by micro-vias. In the method described in thispatent, a slurry or suspension of a hydro-thermally prepared nano-powderand solvent is prepared. A suitable bonding material, such as a polymer,is mixed with the nano-powder slurry, to generate a composite mixturewhich is formed into a dielectric layer. The dielectric layer may beplaced upon a conductive layer prior to curing, or conductive layers maybe applied upon a cured dielectric layer, either by lamination ormetallization processes, such as vapor deposition or sputtering.

In U.S. Pat. No. 6,544,651, entitled “High Dielectric ConstantNano-Structure Polymer-Ceramic Composite” and issued Apr. 3, 2003, thereis described a polymer-ceramic composite having high dielectricconstants formed using polymers containing a metal acetylacetonate(acacs) curing catalyst. In particular, a certain percentage of Co (III)may increase the dielectric constant of a certain epoxy. The highdielectric polymers are combined with fillers, preferably ceramicfillers, to form two phase composites having high dielectric constants.Composites having about 30 to about 90% volume ceramic loading and ahigh dielectric base polymer, preferably epoxy, were apparently found tohave dielectric constants greater than about 60. Composites havingdielectric constants greater than about 74 to about 150 are alsomentioned in this patent. Also mentioned are embedded capacitors withcapacitance densities of at least 25 nF/cm.sup.2, preferably at least 35nF/cm.sup.2, most preferably 50 nF/cm.sup.2.

In U.S. Pat. No. 6,524,352, entitled “Method Of Making A ParallelCapacitor Laminate” and issued Feb. 25, 2003, there is defined aparallel capacitor structure capable of forming an internal part of alarger circuit board or the like structure to provide capacitancetherefore. Alternatively, the capacitor may be used as aninter-connector to interconnect two different electronic components(e.g., chip carriers, circuit boards, and even semiconductor chips)while still providing desired levels of capacitance for one or more ofsaid components. The capacitor includes at least one internal conductivelayer, two additional conductor layers added on opposite sides of theinternal conductor, and inorganic dielectric material (preferably anoxide layer on the second conductor layer's outer surfaces or a suitabledielectric material such as barium titanate applied to the secondconductor layers). Further, the capacitor includes outer conductorlayers atop the inorganic dielectric material, thus forming a parallelcapacitor between the internal and added conductive layers and the outerconductors.

In U.S. Pat. No. 6,446,317, entitled “Hybrid Capacitor And Method OfFabrication Therefore”, and issued Sep. 10, 2002, there is described ahybrid capacitor associated with an integrated circuit package thatprovides multiple levels of excess, off-chip capacitance to die loads.The hybrid capacitor includes a low inductance, parallel plate capacitorwhich is embedded within the package and electrically connected to asecond source of off-chip capacitance. The parallel plate capacitor isdisposed underneath a die, and includes a top conductive layer, a bottomconductive layer, and a thin dielectric layer that electrically isolatesthe top and bottom layers. The second source of off-chip capacitance isa set of self-aligned via capacitors, and/or one or more discretecapacitors, and/or an additional parallel plate capacitor. Each of theself-aligned via capacitors is embedded within the package, and has aninner conductor and an outer conductor. The inner conductor iselectrically connected to either the top or bottom conductive layer, andthe outer conductor is electrically connected to the other conductivelayer. The discrete capacitors are electrically connected to contactsfrom the conductive layers to the surface of the package. Duringoperation, one of the conductive layers of the low inductance parallelplate capacitor provides a ground plane, while the other conductivelayer provides a power plane.

In U.S. Pat. No. 6,395,996, entitled “Multi-layered Substrate WithBuilt-In Capacitor Design” and issued May 28, 2002, there is described amulti-layered substrate having built-in capacitors which are used todecouple high frequency noise generated by voltage fluctuations betweena power plane and a ground plane of a multi-layered substrate. At leastone kind of dielectric material, which has filled-in through holesbetween the power plane and the ground plane and includes a highdielectric constant, is used to form the built-in capacitors.

In U.S. Pat. No. 6,370,012, entitled “Capacitor Laminate For Use In APrinted Circuit Board And As An Inter-connector” and issued Apr. 9,2002, there is described a parallel capacitor structure capable offorming an internal part of a larger circuit board or the like structureto provide capacitance therefore. Alternatively, the capacitor may beused as an inter-connector to interconnect two different electroniccomponents (e.g., chip carriers, circuit boards, and even semiconductorchips) while still providing desired levels of capacitance for one ormore of said components. The capacitor includes at least one internalconductive layer, two additional conductor layers added on oppositesides of the internal conductor, and inorganic dielectric material(preferably an oxide layer on the second conductor layer's outersurfaces or a suitable dielectric material such as barium titanateapplied to the second conductor layers). Further, the capacitor includesouter conductor layers atop the inorganic dielectric material, thusforming a parallel capacitor between the internal and added conductivelayers and the outer conductors.

In U.S. Pat. No. 6,242,282, entitled “Circuit Chip Package andFabrication Method”, issued Jun. 5, 2001, there is described a methodfor packaging a chip which includes the steps of providing aninterconnect layer including insulative material having a first side anda second side, initial metallization patterned on second side metallizedportions of the second side and not on second side non-metallizedportions of the second side, a substrate via extending from the firstside to one of the second side metallized portions, and a chip viaextending from the first side to the second side non-metallized portion.The method also includes positioning a chip on the second side with achip pad of the chip being aligned with the chip via, and patterningconnection metallization on selected portions of the first side of theinterconnect layer and in the via so as to extend to the second sidemetallized portion and to the chip pad. About the chip is molded a“substrate” or other dielectric material.

In U.S. Pat. No. 6,207,595, entitled “Laminate and Method of ManufactureThereof”, issued Mar. 27, 2001, there is described a fabric-resindielectric material for use in a laminate structure and method of itsmanufacture. The resulting structure is adaptable for use in a printedcircuit board or chip carrier substrate. The resin may be an epoxy resinsuch as is currently used on a large scale worldwide for “FR-4”composites. A resin material based on bismaleimide-triazine (BT) is alsoacceptable, this patent further adding that more preferably, the resinis a phenolically hardenable resin material as is known in the art, witha glass transition temperature of about 145 degrees Celsius (C.).

In U.S. Pat. No. 6,150,456, entitled “High Dielectric Constant FlexiblePolyimide Film And Process Of Preparations, issued Nov. 21, 2000, thereis described a flexible, high dielectric constant polyimide filmcomposed of either a single layer of an adhesive thermoplastic polyimidefilm or a multilayer polyimide film having adhesive thermoplasticpolyimide film layers bonded to one or both sides of the film and havingdispersed in at least one of the polyimide layers from 4 to 85 weight %of a ferroelectric ceramic filler, such as barium titanate orpolyimide-coated barium titanate, and having a dielectric constant offrom 4 to 60. The high dielectric constant polyimide film can be used inelectronic circuitry and electronic components such as multilayerprinted circuits, flexible circuits, semiconductor packaging and buried(internal) film capacitors

In U.S. Pat. No. 6,084,306, entitled “Bridging Method of Interconnectsfor Integrated Circuit Packages”, issued Jul. 4, 2000, there isdescribed an integrated circuit package having first and second layers,a plurality of routing pads being integral with the first layer, aplurality of upper and lower conduits, respectively, disposed on theupper and lower surfaces of the first layer, one of the upper conduitselectrically connected to one of the lower conduits, a plurality of padsdisposed on the second layer, vias that electrically connect the pads tothe lower conduits and a chip adhered to the second layer having bondingpads, at least one of which is electrically connected to one of therouting pads.

In U.S. Pat. No. 6,068,782, entitled “Individual Embedded Capacitors ForLaminated Printed Circuit Boards” and issued May 30, 2000, there isdescribed a method of fabricating individual, embedded capacitors inmultilayer printed circuit boards. The method is allegedly compatible ofbeing performed using standard printed circuit board fabricationtechniques. The capacitor fabrication is based on a sequential build-uptechnology employing a first pattern-able insulator. After patterning ofthe insulator, pattern grooves are filled with a high dielectricconstant material, typically a polymer/ceramic composite. Capacitancevalues are defined by the pattern size, thickness and dielectricconstant of the composite. Capacitor electrodes and other electricalcircuitry can be created either by etching laminated copper, by metalevaporation or by depositing conductive ink.

In U.S. Pat. No. 5,831,833, entitled “Bare Chip Mounting Printed CircuitBoard and a Method of Manufacturing Thereof by Photo-etching”, issuedNov. 3, 1998, there is described a method of manufacturing a “bare chip”multi-layer printed circuit board in which arbitrary numbers of wiringcircuit conductor layers and insulating layers are alternately stackedon one or both surfaces of a printed circuit board as a substrate, and arecessed portion with an upper opening capable of mounting andresin-encapsulating a bare chip part is formed on the surface of theprinted circuit board. In what appears to be the preferred embodiment,one of the insulating layers is made from a photosensitive resin, andthe bare chip part mounting recessed portion is formed by photo-etchingthe insulating layer made from the photosensitive resin.

In U.S. Pat. No. 5,426,263, entitled “Electronic Assembly Having aDouble-sided Leadless Component”, issued Jun. 20, 1995, there isdescribed an electronic assembly which has a double-sided leadlesscomponent and two printed circuit boards. The component has a pluralityof electrical terminations or pads on both opposing major surfaces. Eachof the printed circuit boards has a printed circuit pattern that has aplurality of pads that correspond to the electrical terminations on bothsides of the double-sided leadless component. The electrical terminalson one side of the component are attached to the pads on the first boardand the electrical terminals on the other side of the leadless componentare attached to the pads on the second board. The printed circuit boardsare joined together to form a multilayered circuit board so that thedouble-sided leadless component is buried or recessed inside. Thecomponent is attached to the pads of the printed circuit board usingsolder.

In U.S. Pat. No. 5,280,192, entitled “Three-dimensional Memory CardStructure With Internal Direct Chip Attachment”, issued Jan. 18, 1994,there is described a card structure which includes an internal threedimensional array of implanted semiconductor chips. The card structureincludes a power core and a plurality of chip cores. Each chip core isjoined to the power core on opposite surfaces of the power core, andeach chip core includes a compensator core having a two dimensionalarray of chip wells. Each chip well allows for a respective one of thesemiconductor chips to be implanted therein. Further, a compliantdielectric material is disposed on the major surfaces of the compensatorcore except at the bottoms of the chip wells. The compliant dielectricmaterial has a low dielectric constant and has a thermal coefficient ofexpansion compatible with those of the semiconductor chips and thecompensator core, so that thermal expansion stability with the chips andthe compensator core is maintained.

In U.S. Pat. No. 5,162,977, entitled “Printed Circuit Board Having AnIntegrated Decoupling Capacitive Element” and issued Nov. 10, 1992,there is described a PCB which includes a high capacitance powerdistribution core, the manufacture of which is compatible with standardprinted circuit board assembly technology. The high capacitance coreconsists of a ground plane and a power plane separated by a planarelement having a high dielectric constant. The high dielectric constantmaterial is typically glass fiber impregnated with a bonding material,such as epoxy resin loaded with a ferroelectric ceramic substance havinga high dielectric constant. The ferroelectric ceramic substance istypically a nano-powder combined with an epoxy bonding material.According to this patent, the resulting capacitance of the powerdistribution core is sufficient to totally eliminate the need fordecoupling capacitors on a PCB. Use of pre-fired and ground ceramicnano-powders in the dielectric layer poses obstacles for the formationof thru-holes (conductive holes permitting electronic communicationbetween conductive layers of a PCB), however. Pre-fired and groundceramic nano-powder particles have a typical dimension in the range of500-20,000 nanometers (nm). Furthermore, the particle distribution inthis range is generally rather broad, meaning that there could be a10,000 nm particle alongside a 500 nm particle. The distribution withinthe dielectric layer of particles of different size often presents majorobstacles to thru-hole formation where the thru-holes are of extremelysmall diameter, also referred to in the industry as micro-vias due tothe presence of the larger particles. Another problem associated withpre-fired ceramic nano-powders is the ability for the dielectric layerto withstand substantial voltage without breakdown occurring across thelayer. Typically, capacitance layers within a PCB are expected towithstand at least 300 volts (V) in order to qualify as a reliablecomponent for PCB construction. The presence of the comparatively largerceramic particles in pre-fired ceramic nano-powders within a capacitancelayer prevents extremely thin layers from being used because theboundaries of contiguous large particles provide a path for voltagebreakdown. This is even further undesirable because, as indicated by theequation cited above, greater planar capacitance may also be achieved byreducing the thickness of the dielectric layer. The thickness is thuslimited by the size of the particles therein.

In U.S. Pat. No. 5,099,309, entitled “Three-dimensional Memory CardStructure With Internal Direct Chip Attachment”, issued Mar. 24, 1992,there is described a memory card structure containing an embedded threedimensional array of semiconductor memory chips. The card structureincludes at least one memory core and at least one power core which arejoined together in an overlapping relationship. Each memory corecomprises a copper-invar-copper (CIC) thermal conductor plane having atwo dimensional array of chip well locations on each side of the plane.Polytetrafluoroethylene (PTFE) covers the major surfaces of the thermalconductor plane except at the bottoms of the chip wells. Memory chipsare placed in the chip wells and are covered by insulating and wiringlevels. Each power core comprises at least one CIC electrical conductorplane and PTFE covering the major surfaces of the electrical conductorplane. Provision is made for providing electrical connection pathwaysand cooling pathways along vertical as-well as horizontal planesinternal to the card structure.

In U.S. Pat. No. 5,079,069, entitled “Capacitor Laminate For Use InCapacitive Printed Circuit Boards And Methods Of Manufacture” and issuedJan. 7, 1992, there is described a capacitor laminate which allegedlyserves to provide a bypass capacitive function for devices mounted onthe PCB, the capacitor laminate being formed of conventional conductiveand dielectric layers whereby each individual external device isallegedly provided with capacitance by a proportional portion of thecapacitor laminate and by borrowed capacitance from other portions ofthe capacitor laminate, the capacitive function of the capacitorlaminate being dependent upon random firing or operation of the devices.That is, the resulting PCB still requires the utilization of externaldevices thereon, and thus does not afford the PCB external surface areareal estate savings mentioned above which are desired and demanded intoday's technology.

In U.S. Pat. No. 5,016,085, entitled “Hermetic package for integratedcircuit chips, issued May 14, 1991, there is described a hermeticpackage which has an interior recess for holding a semiconductor chip.The recess is square and set at 45 degrees with respect to therectangular exterior of the package. The package uses ceramic layerswhich make up the package's conductive planes with the interior openingstepped to provide connection points. The lowest layer having a chipopening therein may be left out of the assembly to provide a shallowerchip opening recess. This of course is not the same as an internallyformed capacitance or semiconductor component of the nature describedabove, but it does mention internal ceramic layers for a specifiedpurpose as part of an internal structure.

The teachings of the above patents and cited co-pending applications areincorporated herein by reference, as are the teachings of the patentslisted below.

Generally speaking, with respect to commercially available dielectricpowders which have been used in internal conductive structures such asmentioned in some of the above patents, among these being metaltitanate-based powders (see, e.g., U.S. Pat. No. 6,150,456, citedabove), such powders are known to be produced by a high-temperature,solid-state reaction of a mixture of the appropriate stoichiometricamounts of oxides or oxide precursors (e.g., carbonates, hydroxides ornitrates) of barium, calcium, titanium, and the like. In suchcalcination processes, the reactants are wet-milled to accomplish adesired final mixture. The resulting slurry is dried and fired atelevated temperatures, sometimes as high as 1,300 degrees Celsius (C.),to attain the desired solid state reactions. Thereafter, the firedproduct is milled to produce a powder. Although the pre-fired and grounddielectric formulations produced by solid phase reactions are acceptablefor many electrical applications, these suffer from severaldisadvantages. First, the milling step serves as a source ofcontaminants, which can adversely affect electrical properties. Second,the milled product consists of irregularly shaped fractured aggregateswhich are often too large in size and possess a wide particle sizedistribution, 500-20,000 nm. Consequently, films produced using thesepowders are limited to thicknesses greater than the size of the largestparticle. Thirdly, powder suspensions or composites produced usingpre-fired ground ceramic powders must be used immediately afterdispersion, due to the high sedimentation rates associated with largeparticles. The stable crystalline phase of barium titanate for particlesgreater than 200 nm is tetragonal and, at elevated temperatures, a largeincrease in dielectric constant occurs due to a phase transition. It isthus clear that methods of making PCBs which rely on the advantageousfeatures of using nano-powders as part of the PCB's internal componentsor the like, such as those described in selected ones of the abovepatents, possess various undesirable aspects which are detrimental toproviding a PCB with optimal functioning capabilities when it comes tointernal capacitance or other electrical operation. This is particularlytrue when the desired final product attempts to meet today'sminiaturization demands, including the utilization of high densitypatterns of thru-holes therein.

The present invention, as indicated above, is directed to providinginternal resistors for a circuitized substrate, and, more particularly,to the use of a material for the resistor which includes dielectriccomponents in addition to a metal additive. Use of such additives is animportant aspect of the invention to assure desired dielectric constantsfor the material. Use of metal additives in the manner taught herein isalso considered unobvious because of the well known property of metalsto conduct electricity. As defined herein, however, the additives aresufficiently insulated to prevent adequate contact between particlesthereof, thus preventing undesirable electrical current passage whilestill enabling composition adjustment so as to provide resistances ofdiffering values, depending on the operational requirements needed forthe formed circuit(s) of the substrate. A need exists for providingembedded resistors within circuitized substrates such as PCBs which canbe accomplished in a facile, relatively inexpensive manner and whichassures a final product capable of providing desired circuitresistances. Such a need is particularly significant with respect toPCBs having high density internal thru-holes as defined below. It isbelieved that such structures (products, such as electrical assemblies,PCBs, etc.) adapted for using such materials, would constitutesignificant advancements in the art.

The following patents discuss in particular various resistors and howsame are used, one of these discussing use within electronic packagesincluding circuitized substrates such as discussed herein.

In U.S. Pat. No. 6,740,701, entitled “Resistive Film” and issued May 25,2004, there is described a resistive film for use in a potentiometer.The film is in contact with a movable wiper. The film includes a curedpolymer resin and a cured thermosetting resin. Conductive particles ofcarbon black and graphite are dispersed in the film. The conductiveparticles cause the resins to be electrically resistive. Carbonnano-particles are also dispersed in the film. The nano-particlesincrease the wear resistance of the resistive film and reduce electricalnoise as the wiper moves across the film. In the preparation of anexemplary composition, a polymer solution is made by mixing 10-20 wt.percent of a polymer and 0-10 wt. percent thermosetting resin in 60-80wt. percent N-methyl pyrrolidone, based upon the total composition. Thepolymer is mixed with both the conductive and nano-particles to form apaste with a fine particle size. At this point, surfactants andrheological additives may be added if desired to modify the propertiesof the resistive composition. The particle size range and viscosity ofthe paste is monitored to get a resistive paste suitable for applicationin position sensors. The milling time and milling quantity on the ballmill determines the final particle distribution, size and resultingrheology.

In U.S. Pat. No. 6,500,350, entitled “Formation of Thin Film Resistors”and issued Dec. 31, 2002, there is described a method for forming apatterned layer of resistive material in electrical contact with a layerof electrically conducting material. A three-layer structure is formedwhich comprises a metal conductive layer, an intermediate layer formedof material which is degradable by a chemical etchant, and a layer ofresistive material of sufficient porosity such that the chemical etchantfor the intermediate layer may seep through the resistive material andchemically degrade the intermediate layer so that the resistive materialmay be ablated from the conductive layer wherever the intermediate layeris chemically degraded. A patterned photo-resist layer is formed on theresistive material layer. The resistive material layer is exposed to thechemical etchant for the intermediate layer so that the etchant seepsthrough the porous resistive material layer and degrades theintermediate layer. Then, portions of the resistive material layer areablated away wherever the intermediate layer has been degraded.

In U.S. Pat. No. 6,396,387, entitled “Resistors For ElectronicPackaging” and issued May 28, 2002, there are described thin layerresistors which are formed on an insulating substrate, which resistorsmay be embedded within a printed circuit board. Preferred resistivematerials are homogeneous mixtures of metals, such as platinum, anddielectric materials, such as silica or alumina. Even minor amounts ofdielectric material admixed with a metal significantly increase theresistance of the metal. Preferably, the resistive material is depositedon the insulating substrate by combustion chemical vapor deposition(CCVD). In the case of zero valence metals and dielectric material, thehomogeneous mixture is achieved by co-deposition of the metal anddielectric material by CCVD. To form discrete patches of the resistivematerial, substantially any metal-based resistor material, includingthose based on the noble metals, can be etched away. Thus, a layer ofresistive material may be covered with a patterned resist, e.g., anexposed and developed photo-resist, and exposed portions of theunderlying layer of resistive material etched away. This patent alsodescribes the formation of thin layer resistors including the insulatingsubstrate, discrete patches of a layer of resistive material, andconductive material in electrical contact with spaced-apart locations onthe patches of resistive material layer, such conductive materialproviding for electrical connection of the resistive material patcheswith electronic circuitry. Such structures of insulating material,resistive material, and conductive material may be formed by selectiveetching procedures.

OBJECTS AND SUMMARY OF THE INVENTION

It is, therefore, a primary object of the present invention to enhancethe circuitized substrate art by providing a circuitized substratehaving the advantageous features taught herein, including a new andunique material that may be used as an internal resistor within thesubstrate.

It is another object of the invention to provide a method of making sucha circuitized substrate which can be accomplished in a relatively facilemanner and at relatively low costs.

It is still another object of the invention to provide an electricalassembly capable of using such a circuitized substrate and thusbenefiting from the several advantageous features thereof.

It is yet another object of the invention to provide an informationhandling system capable of utilizing a circuitized substrate as partthereof to thus also benefit from the several advantageous featuresthereof.

It is still another object of the invention to provide a new and uniquematerial that can be used as part of a resistor within a circuitizedsubstrate.

According to one aspect of the invention, there is provided a method ofmaking a circuitized substrate having circuitry including a resistor aspart thereof, the method comprising providing a dielectric layer,forming first and second electrical conductors on the dielectric layer,positioning a quantity of material on the dielectric layer between andin contact with the first and second electrical conductors to form acircuit line of the circuitry, this quantity of material including apolymer resin and a quantity of nano-powders including a mixture of atleast one metal component and at least one ceramic component.

According to another aspect of the invention, there is provided a methodof making a circuitized substrate having circuitry including a resistoras part thereof, the method comprising providing a dielectric layerhaving first and second opposite sides and at least one opening therein,forming first and second electrical conductors on the first and secondopposite sides of said dielectric layer, respectively, positioning aquantity of material within the at least one opening and in contact withboth first and second electrical conductors to form a circuit line ofthe circuitry, the quantity of material including a polymer resin and aquantity of nano-powders including a mixture of at least one metalcomponent and at least one ceramic component.

According to yet another aspect of the invention, there is provided acircuitized substrate comprising a first dielectric layer, first andsecond electrical conductors spacedly positioned on the first dielectriclayer, and a quantity of material on said first dielectric layer incontact with the first and second electrical conductors, this quantityof material including a polymer resin and a quantity of nano-powdersincluding a mixture of at least one metal component and at least oneceramic component. The first and second electrical conductors and thequantity of material form a circuit line, with the quantity of materialbeing a resistor for the circuit line.

According to a further aspect of the invention, there is provided acircuitized substrate comprising a first dielectric layer, first andsecond electrical conductors spacedly positioned on the first dielectriclayer, and a quantity of material on the first dielectric layer incontact with the first and second electrical conductors, this quantityof material including a polymer resin and a quantity of nano-powdersincluding at least one metal coated ceramic component. The first andsecond electrical conductors and the quantity of material form a circuitline, with the quantity of material being a resistor for the circuitline.

According to a still further aspect of the invention, there is provideda circuitized substrate comprising a first dielectric layer, first andsecond electrical conductors spacedly positioned on the first dielectriclayer, and a quantity of material on the first dielectric layer incontact with the first and second electrical conductors, this quantityof material including a polymer resin and a quantity of nano-powdersincluding at least one oxide coated metal component. The first andsecond electrical conductors and the quantity of material form a circuitline, with the quantity of material being a resistor for the circuitline.

According to still another aspect of the invention, there is provided acircuitized substrate comprising a first dielectric layer includingfirst and second opposite sides and an opening therein, first and secondelectrical conductors positioned on the first and second sides of thefirst dielectric layer, respectively, and a quantity of material withinthe opening and in contact with both first and second electricalconductors, this quantity of material including a polymer resin and aquantity of nano-powders including a mixture of at least one metalcomponent and at least one ceramic component. The first and secondelectrical conductors and quantity of material form a circuit line, saidquantity of material being a resistor for said circuit line.

According to yet a further aspect of the invention, there is provided anelectrical assembly comprising a circuitized substrate including a firstdielectric layer, first and second electrical conductors spacedlypositioned on the first dielectric layer, a quantity of material on thefirst dielectric layer in contact with the first and second electricalconductors, this quantity of material including a polymer resin and aquantity of nano-powders including a mixture of at least one metalcomponent and at least one ceramic component. The first and secondelectrical conductors and quantity of material form a circuit line, withthe quantity of material being a resistor for said circuit line. Theassembly also includes at least one electrical component positioned onand electrically coupled to the circuitized substrate.

According to still another aspect of the invention, there is provided aninformation handling system comprising a housing, a circuitizedsubstrate positioned substantially within the housing and including afirst dielectric layer, first and second electrical conductors spacedlypositioned on the first dielectric layer, a quantity of material on thefirst dielectric layer in contact with the first and second electricalconductors, the quantity of material including a polymer resin and aquantity of nano-powders including a mixture of at least one metalcomponent and at least one ceramic component. The first and secondelectrical conductors and the quantity of material form a circuit line,with the quantity of material being a resistor for this circuit line.The system further includes at least one electrical component positionedon and electrically coupled to the circuitized substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 are much enlarged, side elevational views which illustrate thebasic steps of making a circuitized substrate according to oneembodiment of the invention;

FIG. 4 is a partial, side elevational view, on approximately the samescale as FIGS. 1-3, which illustrates an example of a multi-layeredcircuitized substrate which can be made using the teachings of theinvention, this substrate including a plurality of thru-holes andadditional dielectric and conductive layers over the relatively simplerembodiment shown in FIG. 1.;

FIG. 4A is a partial, much enlarged side elevational view over the viewsof FIGS. 1-4, which illustrates an alternative embodiment of a resistorwhich may be formed using the teachings of the instant invention;

FIG. 5 is a side elevational view, on a smaller scale than FIGS. 1-4A,showing two examples of circuitized substrates which can be manufacturedusing the teachings of the instant invention; and

FIG. 6 is a perspective view of an information handling system adaptedfor using one or more of the circuitized substrates of the instantinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

For a better understanding of the present invention, together with otherand further objects, advantages and capabilities thereof, reference ismade to the following disclosure and appended claims in connection withthe above-described drawings. Like figure numbers are used from FIG. toFIG. to identify like elements in these drawings.

By the term “circuitized substrate” as used herein is meant to includesubstrates having at least one (and preferably more) dielectric layerand at least one (and preferably more) metallurgical conductivelayer(s). Examples include structures made of dielectric materials suchas fiberglass-reinforced epoxy resins (some referred to as “FR-4”dielectric materials in the art), polytetrafluoroethylene (Teflon),polyimides, polyamides, cyanate resins, photo-imageable materials, andother like materials wherein the conductive layers are each a metallayer (e.g., power, signal and/or ground) comprised of suitablemetallurgical materials such as copper, but may include or compriseadditional metals (e.g., nickel, aluminum, etc.) or alloys thereof.Further examples will be described in greater detail herein-below. Ifthe dielectric materials for the structure are of a photo-imageablematerial, it is photo-imaged or photo-patterned, and developed to revealthe desired circuit pattern, including the desired opening(s) as definedherein, if required. The dielectric material may be curtain-coated orscreen-applied, or it may be supplied as dry film. Final cure of thephoto-imageable material provides a toughened base of dielectric onwhich the desired electrical circuitry is formed. An example of aparticularly useful photo-imageable dielectric is ASMDF (AdvancedSoldermask Dry Film). This composition, which is further described inU.S. Pat. No. 5,026,624, which issued Jun. 25, 1991, and U.S. Pat. No.5,300,402, which issued Apr. 25, 1994, includes a solids content of fromabout 86.5 to about 89%, such solids comprising: about 27.44% PKHC, aphenoxy resin; 41.16% of Epirez 5183, a tetrabromobisphenol A; 22.88% ofEpirez SU-8, an octafunctional epoxy bisphenol A formaldehyde novolacresin; 4.85% UVE 1014 photo-initiator; 0.07% ethylviolet dye; 0.03% FC430, a fluorinated polyether nonionic surfactant from 3M Company; 3.85%Aerosil 380, an amorphous silicon dioxide from Degussa to provide thesolid content. A solvent is present from about 11 to about 13.5% of thetotal photo-imageable dielectric composition. The dielectric layerstaught herein may be typically about 2 mils to about 4 mils thick, butalso thicker or thinner if desired. Examples of circuitized substratesinclude printed circuit boards (or cards) and chip carriers when theafore-mentioned fiberglass-reinforced epoxy resins,polytetrafluoroethylene (Teflon), polyimides, polyamides, cyanate resinsand photo-imageable materials are used as the dielectric material. It isbelieved that the teachings of the instant invention are also applicableto what are known as “flex” circuits (which use dielectric materialssuch as polyimide) and those which use ceramic or other non-polymer typedielectric layers, one example of the latter being what are referred toas multi-layered ceramic (MLC) modules adapted for having one or moresemiconductor chips mounted thereon.

By the term “doped manganite” as used herein is meant manganites thatpossess colossal magnetoresistance properties. These includeperovskite-type oxides of the formula R_(1x) ³⁺A_(x) ²⁺Mn_(1-x) ³⁺Mn_(x)⁴⁺O₃, where R=La, Ce, Nd, Pr, Sm, etc. and A=Ca, Sr or Ba, andcombinations or mixtures thereof.

By the term “electrical assembly” is meant at least one circuitizedsubstrate as defined herein in combination with at least one electricalcomponent electrically coupled thereto and forming part of the assembly.Examples of known such assemblies include chip carriers which include asemiconductor chip as the electrical component, the chip usuallypositioned on the substrate and coupled to wiring (e.g., pads) on thesubstrate's outer surface or to internal conductors using one or morethru-holes. Perhaps the most well known such assembly is theconventional printed circuit board (PCB) typically having severalexternal components such modules (including one or more chip carriers),semiconductor chips, etc. mounted thereon and coupled to the internalcircuitry of the PCB.

By the term “electrical component” as used herein is meant componentssuch as semiconductor chips and the like which are adapted for beingpositioned on the external conductive surfaces of such substrates andelectrically coupled to the substrate for passing signals from thecomponent into the substrate whereupon such signals may be passed on toother components, including those mounted also on the substrate, as wellas other components such as those of a larger electrical system whichthe substrate forms part of.

By the term “ferroelectric ceramic” as used herein is meant ceramicsthat possess ferroelectric properties. These include barium titanate,substituted barium titanate, strontium titanate, lead titanate, leadzirconate titanate, substituted lead zirconate titanate, lead magnesiumniobate, lead zinc niobate, lead iron niobate, solid solutions of leadmagnesium niobate and lead titanate, solid solutions of lead zincniobate and lead titanate, lead iron tantalite, other ferroelectrictantalates, and combinations or mixtures thereof.

By the term “high surface area ceramic” as used herein is meant ceramicsthat possess low-tap density. These include silica, doped silica, silicabased composites, titania, doped titania, titania based composites,alumina, doped alumina, alumina based composites, zinc oxide, doped zincoxide, zinc oxide based composites, and combinations or mixturesthereof.

By the term “information handling system” as used herein shall mean anyinstrumentality or aggregate of instrumentalities primarily designed tocompute, classify, process, transmit, receive, retrieve, originate,switch, store, display, manifest, measure, detect, record, reproduce,handle or utilize any form of information, intelligence or data forbusiness, scientific, control or other purposes. Examples includepersonal computers and larger processors such as servers, mainframes,etc. Such systems typically include one or more PCBs, chip carriers,etc. as integral parts thereof. For example, a PCB typically usedincludes a plurality of various components such as chip carriers,capacitors, resistors, modules, etc. mounted thereon. One such PCB canbe referred to as a “motherboard” while various other boards (or cards)may be mounted thereon using suitable electrical connectors.

By the term “metal-coated ceramic” as used herein is meant ceramicparticles that possess a metal nano surface coating. These includemetal-coated: silica; doped silica; silica-based composites; titania;doped titania; titania-based composites; alumina; doped alumina;alumina-based composites; zinc oxide; doped zinc oxide; zinc oxide-basedcomposites; and combinations or mixtures of such metal-coated materials.Metal nano surface coating materials include gold, silver, aluminum,palladium, platinum, rhodium, and combinations or mixtures thereof.

By the term “oxide coated metal” as used herein is meant metal particlesthat possess an oxide nano surface coating. Examples of such metalsadapted for having such oxide coatings include gold, silver, aluminum,palladium, platinum, rhodium, and combinations or mixtures thereof.Examples of such oxides include silica, doped silica, silica-basedcomposites, titania, doped titania, titania-based composites, alumina,doped alumina, alumina-based composites, zinc oxide, doped zinc oxide,zinc oxide-based composites, and combinations or mixtures thereof.

By the term “thru-hole” as used herein is meant to include what are alsocommonly referred to in the industry as “blind vias” which are openingstypically from one surface of a substrate to a predetermined distancetherein, “internal vias” which are vias or openings located internallyof the substrate and are typically formed within one or more internallayers prior to lamination thereof to other layers to form the ultimatestructure, and “plated through holes” (also known as PTHS), whichtypically extend through the entire thickness of a substrate. All ofthese various openings form electrical paths through the substrate andoften include one or more conductive layers, e.g., plated copper,thereon. These openings are formed typically using mechanical drillingor laser ablation.

By the term “transparent oxide” as used herein is meant oxides that aretransparent in the visible wavelength spectrum. These include tindioxide, indium tin oxide, and combinations or mixtures thereof.

In FIG. 1, a layer 11 of dielectric material is provided, this materialselected from one of the above listed. Atop this layer is at least oneelectrical conductor 13, preferably of copper or copper alloy. In oneembodiment, conductor 13 is formed from a larger sheet of materialbonded (e.g., laminated in solid sheet form using conventional PCBprocessing) to layer 11 and then subjected to known photolithographicprocessing used in the PCB industry, to finally define the conductor'sconfiguration. Alternatively, conductor 13 may be formed usingconventional sputtering operations in which a seed layer is typicallyprovided following which at least one conductive layer is sputteredthere-over. In these embodiments, layer 11 may possess a thickness offrom about one mil to about twenty mils (a mil being one-thousandths ofan inch) while conductor 13 may include a thickness of from about 0.2mils to about 2.5 mils. As understood from the following, conductor 13is to form part of a circuit line for the invention.

The next step, optional but preferred if an additional dielectric layeris to be secured atop conductor 13 (following processing as definedhereinbelow) to form additional circuitry (also preferred), such asshown in FIG. 4, involves treating conductor 13 to enhance the adhesionof the surface thereof, for the purpose of providing increased adhesionfor the subsequently deposited dielectric. To accomplish this, it ispreferred to subject the exposed, upper surface to an oxide (oroxidation) alternative process. One good example of such a processinvolves exposing the conductor to what is referred to as a “BondFilm”solution currently available on the marketplace under this name fromAtotech Deutschland GmbH, an international company having a U.S.A.business address at 1750 Overview Drive, Rock Hill, S.C. BondFilmsolution is comprised primarily of three components: (1) sulfuric acid;(2) hydrogen peroxide; and (3) copper, as well as additional AtotechDeutschland GmbH proprietary constituents. As stated, this process isalso referred to as an oxide alternative process, meaning that it doesnot result in the formation of oxide layers on the treated material. Byway of example, the RMS roughness (a standard measurement means) valuefor the upper surface of conductor 13 after subjecting to the BondFilm“process” may be about 0.6 microns with a peak of about 1.2 to about 2.2microns. The BondFilm process involves immersing the conductor in thesolution for a period of from about 5 to about 120 seconds at a solutiontemperature of about 20 to 35 degrees Celsius (C.). As part of thistreatment, the external surfaces of the conductor are initially cleanedand degreased, following which a micro-etch of the surface occurs.Finally, a thin organic coating is applied. In one example, this thinorganic coating is benzotriazole and possesses a thickness of from about50 Angstroms to about 500 Angstroms. This thin coating remains on theexternal surfaces of the conductor during subsequent processing. Becauseit is so thin, it is not shown in the drawings. Other examples ofalternative oxide processes which can be utilized with the invention areknown in the industry and further description is not deemed necessary.

In FIG. 2, conductor 13 is processed to form at least two conductors 15and 17, spaced apart from each other as shown. By the term “spacedapart” means these conductors are not in physical contact with oneanother. The spacing shown in FIG. 2 is not, therefore, a hole or otheropening within a solid structure. A preferred method of providing suchspacing is to subject the conductor 13 to conventional photolithographicprocessing in which photo-resist is applied, patterned and developed(removed in selected locations). An etchant (e.g., cupric chloride) isthen applied to the exposed surfaces and the material therein is etchedaway. Finally, a rinse (e.g., de-ionized water) is used to wash away thematerial and any residue. Spacing 19 is the result. Although only onespacing 19 is shown in FIG. 2, it is understood that in a preferredembodiment, several such spacings (and resulting resistors) may beformed atop dielectric 11. As such, there would be several pairs ofspaced conductors, each of which may in turn be an end of a line (or“trace” as often described in the substrate art) which forms a circuitline for the final substrate. As understood, several such circuit lines(and resistors) may be simultaneously formed using the teachings of theinvention. In one more specific example, it is possible to form as manyas 10,000 circuit lines including resistors as part thereof within asingle layer of a circuit board.

In FIG. 3, a quantity of resistor material 21 is deposited withinopening 19, preferably using screen or stencil printing. Severalexamples of this material are provided in detail below. Briefly, thismaterial comprises a polymer resin (e.g., a cycloaliphatic epoxy resin)and a quantity of nano-powders including a metal component (e.g.,silver) and a ceramic component (e.g., barium titanate). If the ceramicis a ferroelectric ceramic, a preferred embodiment, the nano-particlespreferably have a particle size substantially within the range of fromabout 0.01 microns to about 0.90 microns and a surface area within therange of from about two to about twenty square meters per gram. Inaddition to barium titanate, other ferroelectric ceramics which can besuccessfully used in this invention include substituted barium titanate,strontium titanate, lead titanate, lead zirconate titanate, substitutedlead zirconate titanate, lead magnesium niobate, lead zinc niobate, leadiron niobate, solid solutions of lead magnesium niobate and leadtitanate, solid solutions of lead zinc niobate and lead titanate, leadiron tantalite, other ferroelectric tantalates, and combinations ormixtures thereof. Metals other than silver may also be used for themetal component, including gold, platinum, copper, nickel, palladium,aluminum and combinations or alloys thereof. One purpose of the metalcomponent in the composition is to establish the resistance of theformed circuit line including the resistor material as part thereof,while further assuring improved electrical characteristics of theresistor (e.g. reduced dielectric loss, improved temperature andfrequency stability, etc.). A secondary purpose of the metal componentis to establish the coefficient of thermal expansion (CTE) of the finalmixture such that the mixture's CTE more closely approximates the CTE ofthe final (laminated) substrate and the conductors to which it isjoined. The addition of the metal component to the mixture is,therefore, a very important feature of this invention. An importantadvantage of such closer CTE values is reduced stress within theresulting laminated substrate during substrate operation.

Significantly, the nano-powders used herein are not fired, and, equallysignificant, are of such a small size and of a surface area so as toenable effective formation of resistive structures (including when usedin openings in the dielectric as shown in FIG. 4A) of such small scalethat high density circuit patterns, including those with thru-holes ofthe type defined above, may be formed. Such thru-holes may be ofextremely small diameter (in one example, as small as one to two mils)to thereby assure such miniaturized, high density circuit patterns. Asindicated, such miniaturization is deemed extremely important withrespect to the designs of many present day circuitized substrates. Inaccomplishing printing of this resistive material, a screen or stencil(not shown) is positioned over conductors 15 and 17 and the material isforced there-though, e.g., using a squeegee or blade. Material 21substantially fills opening 19 and thus physically contacts therespective ends of conductors 15 and 17. Material 21 may also overlapthe ends of the spaced apart conductors 15 and 17 by a sufficientdistance to minimize possible registration errors. In one example, thisoverlap is about 5 mils. In one embodiment, resistor material 21 may bedeposited in paste-like form. However, it is also possible to applymaterial 21 as a liquid, dispensing it through a suitable nozzle (notshown) to fill opening 19. Use of ink jet printing apparatus havingnozzles associated therewith may be used for this. Following dispense,material 21 is now “B-staged” to raise it to a more hardened state thanas so dispensed. The resulting metal particles of resistor material 21so formed may thus include an oxide coating thereon or may include acoating of the polymer resin material which forms part of thecomposition as defined. As such, these particles do not form a singlecontinuous conductive path through the resistor material 21.

In another example, material 21 may include a polymer resin as definedherein and a quantity of nano-powders including a mixture of at leastone metal component as defined herein and at least one high surface areaceramic component, the nano-particles of the high surface area ceramiccomponent having a particle size substantially within the range of fromabout 0.01 microns to about 10 microns and a surface area within therange of from about 1 to about 1500 square meters per gram. Anotherresistor material adapted for use herein is a material which includes apolymer resin as defined and a quantity of nano-powders that comprise amixture of at least one metal coated ceramic component, thenano-particles of the metal coated ceramic component having a particlesize substantially within the range of from about 0.01 microns to about10 microns. In this embodiment, it is thus understood that the ceramiccomponent is coated with the metal component, to give a mixtureincluding particles of a combined structure of both components. In yetanother embodiment, the resistor material may include a polymer resin ofthe type defined herein and a quantity of nano-powders which include atleast one oxide coated metal component as defined above, thenano-particles of the oxide coated metal component preferably having aparticle size substantially within the range of from about 0.01 micronsto about 10 microns. Another acceptable resistor material for use hereinincludes a polymer resin as defined herein and a quantity ofnano-powders that comprise a mixture of at least one metal component andat least one transparent oxide component. In this mixture, thenano-particles of the transparent oxide component preferably include aparticle size substantially within the range of from about 0.01 micronsto about 10 microns, and a surface area within the range of from about 1to about 100 square meters per gram. Still further, a resistor materialhaving the unique properties defined herein may include a polymer resinas defined herein and a quantity of nano-powders which comprise amixture of at least one metal component and at least one doped manganitecomponent. In such a mixture, the nano-particles of the doped manganitecomponent preferably have a particle size substantially within the rangeof from about 0.01 microns to about 10 microns and a surface area withinthe range of from about 1 to about 100 square meters per gram. For theabove embodiments wherein the material includes at least one metalcomponent and the at least one ceramic component is a ferroelectricceramic or a high surface area ceramic, the mixture may further includea carbon nanotube component.

It is to be understood that the embodiment shown in FIG. 3 representsthe simplest embodiment of the invention. Specifically, in the broadestaspects of this invention, the formed circuitzed substrate (now referredto as numeral 23 in FIG. 3) may include but a single dielectric layerand single circuit line (with one resistor) as part thereof, the circuitline of course adapted for being coupled to added components such assemiconductor chips, capacitors, etc., none of these shown in FIG. 3 butclearly understood to those skilled in the art.

In FIG. 4, there is shown an example of a circuitized substrate 23′according to a preferred embodiment of the invention (one in whichadditional dielectric and conductive layers are utilized). Mostsignificantly, substrate 23′ represents one example of how the internalresistor formed above is now electrically coupled to other elements ofthe substrate so as to function therein as desired. In FIG. 4, a seconddielectric layer 29 is applied over layer 11 (and conductors 15 and 17),preferably using a lamination procedure known in the art. A preferredmaterial for layer 29 is one of those mentioned above. An opening 31 isthen formed, e.g., using a mechanical drill or laser ablation, withinlayer 29 and, significantly, down to the upper surface of one of theconductors 15 and 17 (in FIG. 4, this is to conductor 15). Opening 31 isthen preferably plated with metal 33, e.g., copper, to form a thru-holewithin layer 29 which extends from the layer's upper surface to theupper surface of the lower conductor 15. An additional conductor 35 isnow formed on the upper surface of layer 29, preferably utilizingconventional photolithographic processing known in the PCB industry. Theformed conductive thru-hole is thus electrically coupled to conductor 35and underlying conductor 15, to electrically interconnect bothconductors, and also to couple conductor 35 to conductor 17 throughresistor material 21. In a similar manner, a thru-hole 41 may be formedwithin dielectric layer 11, in addition to yet another additionalconductor 43. Still further dielectric layers and thru-holes (shown inphantom in FIG. 4) may be added, depending on the desired operationalrequirements for the substrate being formed. FIG. 4 thus represents thefact that substrate 23′ may include several dielectric and conductivelayers, the latter preferably being in the form of signal layers withselected resistors therein. It is also possible for one or more of theconductive layers shown to be a power or ground layer, albeit such alayer would not include one or more resistors as part thereof. Insummary, the unique circuitry formed using the teachings herein allowsone or more internal resistors to form part of the circuitry, therebyremoving the need for same on the substrate's external surfaces.

FIG. 4 also shows that one or more components 51 may be positioned onthe upper surface of the substrate 23′ and electrically coupled to theinternal circuitry thereof. In one example, component 51 (only oneshown) may be a semiconductor chip which is solder ball attached to pads53, the solder balls represented by the numeral 55. At least one pad (tothe right) is electrically coupled to a corresponding thru-holethere-under which in turn is part of the defined internal circuitry ofsubstrate 23′. The other pads are understood to also be coupled to otherparts of the substrate circuitry. If substrate 23′ is to serve as a chipcarrier product, it in turn is capable of being electrically coupled toyet another, larger substrate such as a PCB (not shown), using in oneembodiment of the invention a second plurality of solder balls 55′. Ifso used, a second pattern of pads 53′ would be formed on the substrate'sundersurface, these in turn electrically coupled to the substrate'scircuitry. One example of such a connection is represented by thethru-hole shown to the left in the bottom dielectric layer bonded tolayer 11. It is also within the scope of this invention for substrate23′ to itself function as a PCB, with a chip carrier or other electroniccomponent positioned thereon.

It is thus understood with respect to FIG. 4 that many separateresistive couplings are possible with various conductive elements whichform part of or are located on the circuitized substrate. The internalor embedded resistor formed within the substrate is uniquely able toprovide such resistance in a variety of circuit combinations, or,simply, within only one such circuit. It is further understood that theexamples described and shown herein are not meant to limit theinvention, as many additional possibilities exist and are well withinthe scope of one skilled in the art.

FIG. 4A represents an alternative embodiment of a resistor of theinvention. Instead of a thru-hole formed within layer 29, as shown inFIG. 4, an opening 71 is formed (e.g., drilled as described above)through the dielectric material of this layer. Rather than plate theinternal walls, a quantity of the resistor material 21 may be depositedwithin the opening in contact with conductors 15 and 35. As such, aresistor is formed between two different conductive layers of theresulting substrate. Such a resistor may be a single element of acircuit line for the substrate or, as with other resistors formedherein, may be used in series with one or more of such resistors.Several combinations are within the scope of those skilled in the artand further description is not deemed necessary.

FIG. 5 represents examples of the structures defined herein-above, thestructure referenced by the numeral 105 being a chip carrier, while thestructure represented by the numeral 107 is a PCB. Each is capable ofincluding one or more internal resistors of the type defined above aspart thereof. Both such PCB and chip carrier assemblies are produced andsold by the Assignee of the invention. In the embodiment (assembly) ofFIG. 5, the chip carrier 105 is mounted on and electrically coupled toPCB 107 using a plurality of solder balls 95′ (preferably ofconventional tin-lead composition as are solder ball connections 55 and55′ in FIG. 4), the chip carrier 105 in turn having a semiconductor chip109 positioned thereon and electrically coupled to the carrier using thesecond plurality of solder balls 95″ (also preferably of conventionaltin-lead composition). The assembly in FIG. 5 may also include a heatsink 110 thermally coupled to the chip 109, e.g., using a conductivepaste 111, and positioned on the upper surface of carrier 105 byappropriate standoffs 113, as is known in the art. It is also within thescope of those skilled in the art to utilize an encapsulant material(not shown) to substantially encase the chip and also to possiblyeliminate the need for the heat sink if such an encapsulant material isused. Encapsulant material is also possible about the lower pluralitiesof solder balls 95′ and 95″. It is even further within the scope of theinvention to couple chip 109 using conventional wire-bonding in which aplurality of fine wires (not shown) are bonded between chip conductorsites and corresponding conductor pads on the underlying substrate.

In FIG. 6, there is shown an information handling system 121 which ispreferably a personal computer, a mainframe computer or a computerserver. Other types of information handling systems known in the art ofthis type may also utilize the teachings of this invention. Thecircuitized substrate or substrates as formed in accordance with theteachings herein, each including one or more internal resistors astaught above, may be utilized in the system 121 as a PCB 107 (shownhidden) and/or a chip carrier 105 (also shown hidden). The circuitizedsubstrates may be utilized as a “mother board” in system 121 or as oneor more individual PCBs typically utilized in such systems. As is known,systems 121 are usually contained within a suitable metal or insulativehousing such as shown by the numeral 123, with appropriate venting (ifdesired) therein, as well as instrumentation externally accessible forsystem operation by the system's designated operator. The remainingelements of information handling systems of these types are known in theart and further description is not believed necessary.

The following Examples represent various combinations of resistormaterials and processes used to form resistors according to variousaspects of the invention. These are understood to be examples only andnot limiting of the scope of this invention.

EXAMPLE ONE

38.5 grams (gm) of an epoxy novolac resin sold under the product name“LZ 8213” from Huntsman, Salt Lake City, Utah, containing about 35 wt %methyl ethyl ketone and 6.5 gm of a phenoxy resin sold under the productname “PKHC” from Phenoxy Associates, Rock Hill, S.C., containing 50 wt %methyl ethyl ketone was mixed together with 100 gm of barium titanate(BaTiO3) powder available from Cabot Corporation, Boyertown, Pa. ((50 gmBaTiO3 with mean particle size=0.065 micron, surface area=16 m2/gm) and(50 gm BaTiO3 with mean particle size=0.12 micron, surface area=8.2m2/gm)), 13 gm propylene glycol methyl ether acetate) and 12 gm methylethyl ketone) and ball milled for 3 days. After 3 days of ball milling,a homogeneous slurry was observed. 50 gm of this mixed slurry was thenmixed with 30 gm silver nano-powders available from Cima NanoTech, Inc.,North Industrial Park, Caesarea, Israel, having a D90 particle size of0.07 micron (D90 meaning 90% of the particles have a diameter less thanor equal to 0.07 micron) and 20 gm methyl ethyl ketone, and ball milledfor 5 days. This mixed composite was then deposited on a dielectricsubstrate surface between and in contact with two conductors and driedat approximately 140° C. for 3 minutes in an oven to remove residualorganic solvents. This was followed by curing in an oven at 190° C. for2 hours. The resulting material possessed a volume resistivity of about1×10⁻⁴ ohm-cm.

EXAMPLE TWO

38.5 grams (gm) of an epoxy novolac resin sold under the product name“LZ 8213” from Huntsman, Salt Lake City, Utah, containing about 35 wt %methyl ethyl ketone and 6.5 gm of a phenoxy resin sold under the productname “PKHC” from Phenoxy Associates, Rock Hill, S.C., containing 50 wt %methyl ethyl ketone was mixed together with 100 gm of barium titanate(BaTiO3) powder available from Cabot Corporation, Boyertown, Pa. ((50 gmBaTiO3 with mean particle size=0.065 micron, surface area=16 m2/gm) and(50 gm BaTiO3 with mean particle size=0.12 micron, surface area=8.2m2/gm)), 13 gm propylene glycol methyl ether acetate) and 12 gm methylethyl ketone) and ball milled for 3 days. After 3 days of ball milling,an homogeneous slurry was observed. 50 gm of this mixed slurry was thenmixed with 30 gm silver nano-powders available from Cima NanoTech, Inc.,North Industrial Park, Caesarea, Israel, having a D90 particle size of0.07 micron (D90 meaning 90% of the particles have a diameter less thanor equal to 0.07 micron), 1 gm carbon nanotubes, and 20 gm methyl ethylketone, and ball milled for 5 days. This mixed composite was thendeposited on a dielectric substrate surface between and in contact withtwo conductors and dried at approximately 140° C. for 3 minutes in anoven to remove residual organic solvents. This was followed by curing inan oven at 190° C. for 2 hours. The resulting material possessed avolume resistivity of about 5×10⁻⁵ ohm-cm.

EXAMPLE THREE

38.5 grams (gm) of an epoxy novolac resin sold under the product name“LZ 8213” from Huntsman, Salt Lake City, Utah, containing about 35 wt %methyl ethyl ketone and 6.5 gm of a phenoxy resin sold under the productname “PKHC” from Phenoxy Associates, Rock Hill, S.C., containing 50 wt %methyl ethyl ketone was mixed together with 100 gm of barium titanate(BaTiO3) powder available from Cabot Corporation, Boyertown, Pa. ((50 gmBaTiO3 with mean particle size=0.065 micron, surface area=16 m2/gm) and(50 gm BaTiO3 with mean particle size=0.12 micron, surface area=8.2m2/gm)), 13 gm propylene glycol methyl ether acetate) and 12 gm methylethyl ketone) and ball milled for 3 days. After 3 days of ball milling,an homogeneous slurry was observed. 50 gm of this mixed slurry was thenmixed with 30 gm silver nano-powders available from Cima NanoTech, Inc.,North Industrial Park, Caesarea, Israel, having a D90 particle size of0.07 micron (D90 meaning 90% of the particles have a diameter less thanor equal to 0.07 micron), 1 gm surface oxidized Copper(Cu) powder,having a mean particle size of 0.3 micron, and 20 gm methyl ethylketone, and ball milled for 5 days. This mixed composite was thendeposited on a dielectric substrate surface between and in contact withtwo conductors and dried at approximately 140° C. for 3 minutes in anoven to remove residual organic solvents. This was followed by curing inan oven at 190° C. for 2 hours. The resulting material possessed avolume resistivity of about 4×10⁻⁴ ohm-cm.

EXAMPLE FOUR

22 gm of the above Cabot BaTiO3 powder, having a mean particle size of0.12 micron and surface area of about 8.2 m²/gm, and 16 gm of Cima NanoTech silver nano-powders having a D90 particle size of 0.07 micron wasmixed together with 15 gm of “LZ 8213” epoxy novolac resin containingabout 35 wt % methyl ethyl ketone and 30 gm methyl ethyl ketone, andball milled for 3 days until an homogeneous slurry was observed. Thismixed composite was then deposited on a substrate in contact with twoconductors and dried at approximately 140° C. for 3 minutes in an ovento remove residual organic solvents. This was followed by curing in anoven at 190° C. for 2 hours. The resulting film possessed a volumeresistivity of about 4×10⁻⁴ ohm-cm.

EXAMPLE FIVE

22 gm of the above Cabot BaTiO3 powder, having a mean particle size of0.12 micron and surface area of about 8.2 m²/gm, and 16 gm of Cima NanoTech silver nano-powders having a D90 particle size of 0.07 micron, and2 gm lanthanum calcium manganite (La_(2/3)Ca_(1/3)MnO₃) powder, having amean particle size of 0.02 micron, was mixed together with 15 gm of “LZ8213” epoxy novolac resin containing about 35 wt % methyl ethyl ketoneand 30 gm methyl ethyl ketone, and ball milled for 3 days until anhomogeneous slurry was observed. The mixed composite was then depositedon a substrate in contact with two conductors and dried at approximately140° C. for 3 minutes in an oven to remove residual organic solvents.This was followed by curing in an oven at 190° C. for 2 hours. Theresulting film possessed a volume resistivity of about 1×10⁻³ ohm-cm.

EXAMPLE SIX

22 gm of the above Cabot BaTiO3 powder, having a mean particle size of0.12 micron and surface area of about 8.2 m²/gm, and 16 gm of Cima NanoTech silver nano-powders having a D90 particle size of 0.07 micron and 1gm indium tin oxide powder, having a mean particle size of 0.2 micronwas mixed together with 15 gm of “LZ 8213” epoxy novolac resincontaining about 35 wt % methyl ethyl ketone and 30 gm methyl ethylketone, and ball milled for 3 days until an homogeneous slurry wasobserved. This mixed composite was deposited on a substrate in contactwith two conductors and dried at approximately 140° C. for 3 minutes inan oven to remove residual organic solvents. This was followed by curingin an oven at 190° C. for 2 hours. The resulting film possessed a volumeresistivity of about 5×10⁻⁴ ohm-cm.

EXAMPLE SEVEN

2 gm of fumed silica powder, having an average particle size of 0.016micron and surface area of about 110 m²/gm, and 10 gm of Cima Nano Techsilver nano-powders having a D90 particle size of 0.07 micron was mixedtogether with 8 gm of “LZ 8213” epoxy novolac resin containing about 35wt % methyl ethyl ketone and 20 gm methyl ethyl ketone, and ball milledfor 3 days until an homogeneous slurry was observed. A thin film of thismixed composite was deposited on a substrate between and in contact withtwo spaced conductors and dried at approximately 140° C. for 3 minutesin an oven to remove residual organic solvents. This was followed bycuring in an oven at 190° C. for 2 hours. The resulting film possessed avolume resistivity of about 2.3×10⁻² ohm-cm.

EXAMPLE EIGHT

1.2 gm of the above fumed silica powder, having a average particle sizeof 0.016 micron and surface area of about 110 m²/gm, and 10 gm of CimaNano Tech silver nano-powders having a D90 particle size of 0.07 micronwas mixed together with 8.5 gm of “LZ 8213” epoxy novolac resincontaining about 35 wt % methyl ethyl ketone and 20 gm methyl ethylketone, and ball milled for 1 day until an homogeneous slurry wasobserved. This mixed composite was then deposited on a substrate betweentwo spaced conductors and dried at approximately 140° C. for 3 minutesin an oven to remove residual organic solvents. This was followed bycuring in an oven at 190° C. for 2 hours. The resulting film possessed avolume resistivity of about 1×10⁻² ohm-cm.

EXAMPLE NINE

1 gm of the above fumed silica powder, having an average particle sizeof 0.016 micron and surface area of about 110 m²/gm, was mixed with 100ml gold chloride ethanol solution (0.05 gm gold chloride dissolved in100 ml ethanol). The mixed solution was stirred to deposit gold on thesilica surface. Gold coated silica was then separated using filtrationand washing. 1.2 gm of the fumed silica powder, having an averageparticle size of 0.016 micron and a surface area of about 110 m²/gm, and0.1 gm gold coated silica, and 10 gm of Cima Nano Tech silvernano-powders having a D90 particle size of 0.07 micron was mixedtogether with 8.5 gm of “LZ 8213” epoxy novolac resin containing about35 wt % methyl ethyl ketone and 20 gm methyl ethyl ketone, and ballmilled for 1 day until an homogeneous slurry was observed. This mixedcomposite was deposited on a substrate between two spaced conductors anddried at approximately 140° C. for 3 minutes in an oven to removeresidual organic solvents. This was followed by curing in an oven at190° C. for 2 hours. The resulting film possessed a volume resistivityof about 5×10⁻² ohm-cm.

Thus there has been shown and described a circuitized substrate havingone or more internal resistors as part thereof, which substrate can beformed using many conventional PCB processes to thereby reduce costsassociated with production thereof. There have also been defined severalexamples of resistor materials which can be positioned between twoadjacent conductors as part of such a circuit line to form circuitry forthe substrate. Most significantly, the invention affords the opportunityto vary the resistances between conductors by varying the resistormaterial composition, as represented by the foregoing examples. Suchlatitude greatly assists the circuit designer in meeting varyingoperational requirements.

While there have been shown and described what at present are consideredthe preferred embodiments of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the scope of the invention as defined bythe appended claims. The invention as defined herein is capable oftransmitting both regular and high speed (frequency) signals, the latterat a rate of from about one Gigabits/sec to about ten Gigabits/second,while substantially preventing impedance disruption. It is also capableof being produced using many conventional PCB processes so as to assurereduced cost and facilitate ease of manufacture. That is, the preferredmethod for assembling the circuitized substrate of the inventionpreferably involves the use of conventional lamination processes as partof the method, in which the dielectric layers, having the designatedcircuitry and/or conductive elements (planes) thereon are “stacked up”in aligned manner with one another and subjected to relatively highpressures and temperatures associated with conventional lamination. Ofperhaps greater significance, the invention is able to assure circuitpattern miniaturization as is deemed extremely important with regards tomany of today's design requirements.

1. A circuitized substrate comprising: a first dielectric layer; firstand second electrical conductors spacedly positioned on said firstdielectric layer; a quantity of resistor material positioned on saidfirst dielectric layer in contact with said first and second electricalconductors, said quantity of resistor material including a polymer resinand a quantity of non-fired nano-powders including a mixture of at leastone metal component and at least one ferroelectric ceramic component,said nano-powders having a particle size within the range of from about0.01 micron to about 0.9 micron and a surface area within the range offrom about 2 to about 20 square meters per gram, said particles of saidmetal component including a coating of said polymer resin thereon suchthat said metal particles do not form a single continuous conductivepath through said resistor material; and a second dielectric layerpositioned over said first and second electrical conductors and saidquantity of resistor material such that said quantity of resistormaterial comprises an internal resistor within said substrate.
 2. Thecircuitized substrate of claim 1 wherein each of said first and seconddielectric layers comprises an organic dielectric material selected fromthe group of polymer materials consisting of fiberglass-reinforced epoxyresins, polytetrafluoroethylene, polyimides, polyamides, cyanate resins,polyphenylene ether resins, photo-imageable materials, and combinationsthereof.
 3. The circuitized substrate of claim 1 wherein said first andsecond electrical conductors are each comprised of copper or copperalloy material.
 4. The circuitized substrate of claim 1 furtherincluding a third dielectric layer positioned on said first dielectriclayer opposite said second dieletic layer, and first and secondelectrically conductive layers positioned on said second and thirddielectric layers, respectively, said first and second electricallyconductive layers being electrically coupled to said first and secondconductors, respectively.
 5. The circuitized substrate of claim 4further including an opening within said second dielectric layer betweensaid first electrical conductor and said first conductive layer and asecond quantity of said resistor material therein, said second quantityof resistor material within said opening contacting said firstelectrical conductor and said first conductive layer and comprising aninternal resistor within said second dielectric layer.
 6. A circuitizedsubstrate comprising: a first dielectric layer; first and secondelectrical conductors spacedly positioned on said first dielectriclayer; a quantity of resistor material positioned on said firstdielectric layer in contact with said first and second electricalconductors, said quantity of resistor material including a polymer resinand a quantity of non-fired nano-powders including a mixture of at leastone metal component and at least one high surface area ceramiccomponent, said nano-powders having a particle size within the range offrom about 0.01 micron to about 10 microns and a surface area within therange of from about 1 to about 1500 square meters per gram, saidparticles of said metal component including a coating of said polymerresin thereon such that said metal particles do not form a singlecontinuous conductive path through said resistor material; and a seconddielectric layer positioned over said first and second electricalconductors and said quantity of resistor material such that saidquantity of resistor material comprises an internal resistor within saidsubstrate.
 7. The circuitized substrate of claim 6 wherein each of saidfirst and second dielectric layers comprises an organic dielectricmaterial selected from the group of polymer materials consisting offiberglass-reinforced epoxy resins, polytetrafluoroethylene, polyimides,polyamides, cyanate resins, polyphenylene ether resins, photo-imageablematerials, and combinations thereof.
 8. The circuitized substrate ofclaim 6 wherein said first and second electrical conductors are eachcomprised of copper or copper alloy material.
 9. The circuitizedsubstrate of claim 6 further including a third dielectric layerpositioned on said first dielectric layer opposite said seconddielectric layer, and first and second electrically conductive layerspositioned on said second and third dielectric layers, respectively,said first and second electrically conductive layers being electricallycoupled to said first and second conductors, respectively.
 10. Thecircuitized substrate of claim 9 further including an opening withinsaid second dielectric layer between said first electrical conductor andsaid first conductive layer and a second Quantity of said resistormaterial therein, said second quantity of resistor material within saidopening contacting said first electrical conductor and said firstconductive layer and comprising an internal resistor within said seconddielectric layer.